A viscometer based on the damping of a mechanical resonator can be very accurate in theory, but if installation into a fixed location introduces an unknown and immeasurable amount of intrinsic damping (that is, the amount of damping that the viscometer would experience in a vacuum) then that unknowable quantum of intrinsic damping limits accuracy. The essential problem is that of preventing the vibrations of the viscometer's resonator from leaking into the structure holding the viscometer, for example a pipe or the wall of a tank, thereby affecting the level of intrinsic damping.
Some prior art systems have relied on compliant elements such as elastomeric O-rings to isolate the vibrations to the viscometer structure. Unfortunately, the use of such O-rings limits the pressure and temperature range of viscometer usage, thereby limiting the environments in which such a viscometer can be used. Finally, even if everything about the environment (tank walls, pipe or other holding structure) were known, and O-rings that could accommodate a broad range of temperature and pressure were available, it is very difficult to make the installation process perfectly repeatable. Any time screw threads must be tightened, there is the possibility of variation that can introduce an immeasurable quantum of difference.